What feature distinguishes Gueuze from other sour beers?

The distinguishing feature of Gueuze that sets it apart from other sour beers is the combination of fermentable and aged lambics. Gueuze is a blend of young and old lambic beers, which are spontaneously fermented beers typical of the Brussels region of Belgium. The younger lambics provide sweetness and carbonation, while the older lambics contribute complexity and depth of flavor. This blending process and the specific aging of these components create the unique character of Gueuze, characterized by its tartness, funkiness, and often complex, effervescent profile.

In contrast, the other options highlight features that do not accurately represent Gueuze as a style. For instance, the assertion of a single fermentation process does not apply, as Gueuze is specifically defined by its blend of various fermentations. High sweetness is not a characteristic feature, as Gueuze typically exhibits a balance of acidity and dryness rather than pronounced sweetness. Lastly, carbon dioxide is an essential aspect of Gueuze, resulting from the secondary fermentation that occurs during the blending process; thus, the absence of carbonation would be a mischaracterization of this iconic beer style.